Journal of Watershed Management Research

The flow duration curve (FDC) is a classical method used to graphically represent the relationship between the frequency and magnitude of stream flow. Several factors are involved in the shape of (FDC), including climatic and physiographic parameter of basin. In this research, the relationship between (FDC) and the physical parameters of the basin were investigated. 20 hydrometric stations with appropriate daily data were selected. Physiographic parameters extracted using the GIS capability and Flow duration curve were plotted using daily flow data. The first and last inflection of the curve was computed, using coding in MATLAB programming environment. Factor analysis was performed and the most important independent factors influencing the form of flow duration curve were identified. The homogeneous analysis based on independent factors, using cluster analysis method was investigated. Finally correlation between the exceedance values at the inflection point and the geometric and hydrologic parameters were investigated. The results showed that the parameters of the perimeter, Area, length of Main River, length of the catchment, the time of concentration, and the average height of the basin were the most important factors affecting the shape of the curve in the study area. All above mentioned parameters has a positive correlation with deformation curve Index. Precipitation was found as the second most influential factor, with a negative correlation.